The present invention relates to a side airbag apparatus that protects an occupant seated in a vehicle seat from an impact by deploying and inflating an airbag on a side of the occupant when the impact is applied to a vehicle.
A side airbag apparatus is widely known for protecting an occupant from an impact when the impact is applied to an automobile from a side to an automobile seat in which the occupant is seated, for example, due to a side collision. In the side airbag apparatus, an airbag is installed in a seat back of an automobile seat in a folded state together with an inflator.
In the side airbag apparatus, when an impact is applied from the side on a member forming the side portion of an automobile (body side portion) such as a side door, inflation gas is supplied from the inflator into the airbag so that the airbag is deployed and inflated. The airbag is projected from the automobile seat with a part of the airbag remaining in the seat back. The airbag continues being deployed and inflated forward in the narrow space between the occupant and the body side portion. The airbag restrains the occupant and reduces the impact that is transmitted from the side to the occupant through the body side portion.
One form of such a side airbag apparatus is disclosed in US Patent Application Publication No. 2006/0202450. The side airbag apparatus of the publication includes an airbag, which is divided into an upstream-side inflation chamber and a downstream-side inflation chamber by a vertical partition having a communication hole. The upstream-side inflation chamber receives inflation gas from an inflator, and the downstream-side inflation chamber, which is adjacent to the front side of the upstream-side inflation chamber, receives the inflation gas via the communication hole.
In this side airbag apparatus, when the inflator discharges inflation gas in response to an impact, the inflation gas is first supplied to the upstream-side inflation chamber so that the upstream-side inflation chamber starts being deployed and inflated. The upstream-side inflation chamber restrains the rear half of the upper body of the occupant and protects it from the impact. Before the deployment and inflation of the upstream-side inflation chamber are completed, some of the inflation gas in the upstream-side inflation chamber flows to the downstream-side inflation chamber through the communication hole. The inflation gas starts deploying and inflating the downstream-side inflation chamber with a delay from the upstream-side inflation chamber to restrain the front half of the occupant's upper body, thereby protecting it from the impact.
The side airbag apparatus of the above publication deploys and inflates the downstream-side inflation chamber with a delay from the upstream-side inflation chamber. Thus, the airbag is prevented from being deployed as a whole with momentum. If an obstacle exists in front of the airbag, the obstacle will not be thrust by the airbag.
However, the communication hole connecting the upstream-side inflation chamber and the downstream-side inflation chamber with each other is always open. Therefore, the inflation gas in the upstream-side inflation chamber flows into the downstream-side inflation chamber via the communication hole at a relatively early stage of the deployment and inflation of the upstream-side inflation chamber. Thus, the effect of preventing an obstacle from being thrust is less than satisfactory. Hence, the configuration is not applicable to a case in which a greater effect is sought.
Such a drawback is not limited to a case in which the side airbag apparatus is installed in an automobile, but applies to cases in which the apparatus is installed in any type of vehicle.